Mordanted photographic imbibition dye printing blank



United States Patent 2,952,566 MORDANTED PHOTOGRAPHIC IMBIBITION DYE PRINTING BLANK Louis M. Condax, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Oct. 30, 1956, Ser. No. 619,138 1 Claim. (Cl. 117-83) This invention relates to the art of photography and more particularly to mordanted imbibition dye printing blanks for use in the imbibition dye printing process.

In the imbibition dye printing process of photography the conventional process involves the transfer of a dye imagewise from an imbibition dye printing matrix, such as a gelatin relief image, to an imbibition blank containing a mordant for the dye.

One defect of such mordanted imbibition blanks resides in a distinct tendency for the dyes to diffuse laterally from the dyed matrix to the imbibition blank resulting in poor sharpness in the transferred dye images. Another undesirable effect which has been encountered is the change in appearance of the dye prints made on such blanks between the time the Wet print has been made and when it has dried. Accordingly, it has been necessary for an operator to first dry a color print before an estimate can be made of the amount of color correction to make in the final print. These troubles are attributable in part to the type of mordant used and more particularly to the method of incorporating it into the imbibition dye printing blank as will be seen from consideration of my invention.

I have discovered that if mordants, such as thorium hydroxide, are formed on the surface of a blank in a certain manner the resulting imbibition blank will yield sharper images and the hue shift from the wet to dry state of the prints is materially reduced.

The method which I use to effect the mentioned improvement in imbibition dye printing blanks comprises successively coating on a support, such as a baryta-coated paper or a well-sized paper stock, in any order, an aqueous solution of a hydrophilic organic colloid and thorium nitrate and a second solution of a hydrophilic organic colloid and sodium aluminate sufficiently alkaline to precipitate metal hydroxide when the coatings come in contact with each other. Accordingly, the sodium aluminate may be coated either before or after applying the thorium nitrate to the support. As a result of the use of this technique it appears that the metal hydroxide mordant may be formed much nearer the surface of the paper or in a different form. In any event, dye images are prevented from wandering as attested by photomicrographs showing that more dye is mordanted closer to the surface than when the paper is mordanted by other methods. A resolution test made visually with a contact line screen showed a resolution of as high as 80 lines per inch for a cyan dye image on a paper mordanted with coatings of thorium nitrate followed by sodium aluminate, compared to 40 to 5 6 lines per inch for a similar dye image made on paper mordanted with thorium hydroxide by previous methods.

Also, dye images obtained on the new imbibition blank showed that the hue shift from the wet to dry state had been reduced from about 6 m to 2 mp. An added effect observed was that a cyan dye image formed on the thorium mordanted paper had a peak absorption which was shifted from about 640 to 660 millimicrons making possible the reproduction of a Wider gamut of color.

In a similar manner, other combinations of mordants can be formed on the surface of an imbibition blank, for example, organic base salts and metal salts, e.g., guanidine 2,952,566 Patented Sept. 13, 1960 nitrate with sodium alminate; organic acids or their salts and organic bases or their salts, e.g., tannic acid, sodium salt with guanidine nitrate. However, best results from the viewpoint of image sharpness and hue shift are obtained using the thorium hydroxide mordanted element such as described in more detail in the example hereinafter.

Example The following coatings were applied successively to a gelatin-baryta-coated paper stock:

Coat #1.-Dissolve one pound of dry gelatin in 4 liters of distilled water heated to 110 F. Dissolve 30 grams Th(NO IZH O in 2 liters of water containing 100 cc. of 6 N H Add the thorium nitrate solution slowly to the gelatin solution with stirring. Water and a spreading agent (saponin solution) are then added to the resulting gelatin solution to make a total weight of 18 pounds. This is then coated on the paper base at a coverage of about 16 grams per square foot.

Coat #2.Dissolve one pound of gelatin in 4 liters of distilled water. To the gelatin solution add 115 cc. of 6 N NaOH. Dissolve 60 grams of sodium aluminate in 2 liters of water. When solution is complete, add this with stirring to the previously prepared gelatin solution at about F. When the two solutions are thoroughly mixed, add water to make to final volume weighing about 20 pounds. Coat this gelatin solution directly over first coat at a coverage of about 20 grams per square foot.

The support upon which the mordant. may be formed in the manner described in the above example is not especially critical although absorbent supports, such as baryta-coated photographic paper or well-sized paper stock, is preferred. Cellulose ester film base and synthetic polymer films suitably subbed with, for example, gelatin-containing layers are also useful. Likewise a blushed cellulose ester layer prepared on paper as described in US. Patent 2,207,695 may be used.

The hydrophilic colloid content of the coatings applied to the support can be varied, for example, polyvinyl alcohol, water-soluble gums and preferably gelatin are useful for this purpose.

In applying the two coatings to the support, as described in the example, it is preferred that the first coating be dried before application of the second; however, the second may be coated onto the first shortly thereafter, for example, just after the first coating has set to a gel.

It will be noted that in the above example the sodium aluminate coating was made from a solution sufiiciently alkaline to cause precipitation of metal hydroxide such as thorium hydroxide when the two coatings come into contact.

What I claim is:

A method for preparing a mordanted imbibition dye printing blank which comprises coating a paper support with an aqueous solution of gelatin and thorium nitrate, and coating thereon an aqueous solution of gelatin and sodium alminate sufliciently alkaline to precipitate metal hydroxide on said support when moist coatings of said solutions come into contact.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Fritz Ephraim: A Text-Book of Inorganic Chemistry," published 1934, page 39 

